U.S. patent application number 11/545001 was filed with the patent office on 2007-04-19 for solid-fuel-combustion fire-insulation interface with adjacent container-wall.
Invention is credited to Michael R. Dennis, Russell A. Monk, Thomas S. Ohnstad.
Application Number | 20070084198 11/545001 |
Document ID | / |
Family ID | 37963127 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070084198 |
Kind Code |
A1 |
Ohnstad; Thomas S. ; et
al. |
April 19, 2007 |
Solid-fuel-combustion fire-insulation interface with adjacent
container-wall
Abstract
A solid-fuel rocket assembly including an elongate fuel
container having a long axis, and an inner surface spaced outwardly
from, and generally circumsurrounding, that axis, and a continuous,
elastomeric, heat-insulative, intumescence-behavior jacket adhered
to the container's inner surface and defining a central chamber for
receiving an elongate body of solid fuel. This structure implements
a method for minimizing, in a solid-fuel rocket, heat damage to the
wall of a solid-fuel container during burning of contained solid
fuel including the steps of (a) producing dual-interface,
continuous-presence, heat-insulative barriering in the zone
existing between the container and burning fuel, with such
barriering being characterized by (1) interfacially following any
heat-produced deformations in the container wall, and (2)
interfacially confronting the burning fuel with a tendency for
intumescence-driven barrier-thickening.
Inventors: |
Ohnstad; Thomas S.; (Salem,
OR) ; Dennis; Michael R.; (Scappoose, OR) ;
Monk; Russell A.; (Salem, OR) |
Correspondence
Address: |
ROBERT D. VARITZ, P.C.
4915 SE 33RD PLACE
PORTLAND
OR
97202
US
|
Family ID: |
37963127 |
Appl. No.: |
11/545001 |
Filed: |
October 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60726288 |
Oct 13, 2005 |
|
|
|
Current U.S.
Class: |
60/291 |
Current CPC
Class: |
F42B 39/18 20130101;
F02K 9/346 20130101; B64G 1/403 20130101 |
Class at
Publication: |
060/291 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Claims
1. A solid-fuel rocket assembly comprising an elongate body of
solid rocket fuel having a generally central long axis, and an
outer surface spaced outwardly from, and generally
circumsurrounding, said axis, an elongate fuel container having an
inner surface spaced outwardly from, and generally
circumsurrounding, the fuel body's said outer surface, and a
continuous, elastomeric, heat-insulative, intumescence-behavior
jacket adhered to said container's said inner surface and generally
circumsurrounding said fuel body's said outer surface.
2. The assembly of claim 1, wherein said jacket is formed of a
sprayed-in-place, high-elastomeric material including an embedded
distribution of intumescence elements.
3. The assembly of claim 2, wherein the embedded distribution of
intumescence elements is substantially uniform throughout said
jacket.
4. The assembly of claim 2, wherein the embedded distribution of
intumescence elements is non-uniform, in the sense of possessing a
density gradient which transitions from larger-to-lesser
progressing outwardly in the jacket in a direction extending
through the jacket from adjacent said fuel body toward said
container.
5. The assembly of claim 2, wherein said intumescence elements take
the form of at least one of (a) sodium silicate crystals, (b)
elements of microencapsulated melamine polyphosphates, (c) elements
of amorphous silica, (d) elements of microencapsulated ammonium
polyphosphates, and (e) elements of expandable graphite.
6. The assembly of claim 2, wherein said jacket further includes an
embedded distribution of reinforcing fibres.
7. A solid-fuel rocket assembly comprising an elongate fuel
container having a long axis, and an inner surface spaced from and
generally circumsurrounding said axis, and a continuous,
elastomeric, heat-insulative, intumescence-behavior jacket (a)
adhered to said container's said inner surface, (b) spaced from and
generally circumsurrounding said axis, and (c) defining a central
chamber for receiving an elongate body of solid rocket fuel.
8. A method for minimizing, in a solid-fuel rocket, heat damage to
the wall of a solid-fuel container during burning of contained
solid fuel comprising placing between the container and contained
fuel a structurally continuous, heat-insulative barrier having an
outer surface which is adhered to the container, and an inner
surface which faces the contained solid fuel, and during burning of
the contained fuel, (a) utilizing surface-adherence and material
elasticity in the barrier's outer surface to cause that surface to
follow any heat-created deformations occurring in the adjacent
container wall, and (b) simultaneously utilizing the barrier's
inner surface to confront the burning solid fuel with intumescence
behavior.
9. A method for minimizing, in a solid-fuel rocket, heat damage to
the wall of a solid-fuel container during burning of contained,
inwardly spaced, solid fuel comprising producing dual-interface,
continuous-presence, heat-insulative barriering in the zone
existing intermediate the container and the burning fuel, with such
barriering being characterized by (a) interfacially following any
heat-produced deformations in the container wall, and (b)
interfacially confronting the burning fuel with a tendency for
intumescence-driven barrier-thickening.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to currently pending,
prior-filed U.S. Provisional Patent Application Ser. No.
60/726,288, filed Oct. 13, 2005, for "Solid-Fuel-Combustion
Fire-Insulation Interface With Adjacent Container Wall". The entire
disclosure content of that prior-filed provisional application is
hereby incorporated herein by reference.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] This invention relates to the provision of an elastomeric
and intumescence interface which is capable of providing fire
insulation between a combusting solid fuel material and a nearby
wall of a container which is holding this material. A preferred
embodiment of the invention is described herein in conjunction with
such an interface, and with the creation of such an interface,
which exists between solid fuel which is used in a rocket, and the
surrounding wall, typically the rocket wall itself, which contains
this fuel.
[0003] There are certain situations, such as the one set forth
generally above with respect to a solid-fuel rocket, wherein an
interface or a zone of proximity exists between a solid combustible
fuel material which is combusting during a rocket launch, and a
container wall for that material which needs to be protected
against fire damage and potentially catastrophic destruction during
such fuel combustion.
[0004] In the field of solid-fuel rockets, it is apparently a
conventional practice to line the inside wall of a solid
fuel-containing compartment with an elastomeric sheet material
interface which is referred to, and functions, as an ablative
material. Such sheet material is typically installed the form of in
predefined-outline sheets (i.e., sheets with defined lateral
edges), bonded to the inside surface of the subject wall which is
to be protected, with obvious seams existing where the edges of
adjacent sheets come together. Experience over the years in this
setting has been decorated with a number of catastrophic failures
where, during solid-fuel combustion, the intended protective
sheet-layer which lies between the combusting fuel and the nearby
containing wall fails for one reason or another, perhaps because of
seam failure (i.e., seam opening, and resultant exposure of the
container wall to the extraordinary heat of fuel combustion).
[0005] The present invention provides a resolution to this issue by
furnishing a special elastomeric coating which may be sprayed into
place as one continuous coating which offers no seams for
breaching, and which responds with intumescence behavior (a
material-swelling behavior) in response to exposure to high heat,
such as fuel combustion. This intumescence heat-response behavior
acts quickly, effectively and elastomerically to insulate a
protected wall from the intense combustion heat, such as that which
is experienced during launch in and of a solid fuel rocket. No
coating/layer seams exist to open, and the coating, which follows
natural wall expansion with sympathetic, elastomeric coating
expansion, also grows progressively in thickness, by way of
intumescence behavior, to distance the high-heat fuel-combustion
zone from the vulnerable container wall. Various intumescence
materials, some of which are mentioned herein, and one of
which--sodium silicate--is preferably employed, may be used within
the coating of this invention to invoke the desired
coating-intumescence behavior.
[0006] If desired, the intumescence-armed coating interface of this
invention may additionally be strengthened and stabilized by the
inclusion in the coating of embedded fibrous contents, such as
glass or Kevlar.RTM. strands/whiskers.
[0007] The various important features and advantages which are
offered by the present invention, from both a structural and a
methodologic point of view, will now become more fully apparent as
the detailed invention description which is presented below is read
in conjunction with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a fragmentary, cross-sectional, axial view of a
solid-fuel rocket assembly including a heat-insulative barrier
jacket which, in accordance with the present invention, is
interposed the inside of a container wall for solid fuel in the
assembly, and the solid fuel per se.
[0009] FIG. 2 is an enlarged, fragmentary, cross-sectional detail
of a portion of the assembly shown in FIG. 1 illustrating details
of one form of an insulative jacket material which includes a body
of high-elastomeric material in which there is embedded a relative
uniformly distributed distribution of intumescence elements. A
small region of the jacket material pictured in FIG. 2 is
illustrated with included, embedded reinforcing fibres, such as
Kevlar.RTM..whiskers.
[0010] FIG. 3 is similar to FIG. 2, except that it illustrates a
modified form of heat-insulative jacket material, wherein
intumescence elements are embedded in a high-elastomeric material
with a distributed density gradient, with respect to which a higher
distribution density exists near the location of solid rocket fuel,
and a lesser distribution density exists more closely adjacent the
inner wall of an associated solid fuel container.
[0011] FIGS. 4A, 4B and 4C are story-telling drawings that
generally illustrate relevant intumescence behavior which
characterizes the performance of the invented heat-insulative
jacket during burning of rocket fuel.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Turning attention now to the drawings, and referring first
of all to FIGS. 1 and 2, indicated generally at 10 is a rocket
engine, or assembly, which is made in accordance with a preferred
embodiment of, and manner of practicing, the present invention.
Rocket assembly 10 includes an elongate, cylindrical, rocket-engine
container 12 possessing a cylindrical wall having an inner surface
12a which generally equidistantly circumsurrounds the long axis 12b
of container 12. Axis 12b extends generally into, and normal to,
the plane of FIG. 1 in the drawings.
[0013] Disposed generally centrally within container 12, generally
centrally aligned with long axis 12b in the container, and
possessing a generally cylindrical outer surface 14a, is an
elongate, cylindrical body of solid rocket fuel 14 possessing a
long axis 14b which is substantially coincident with continuer
access 12b.
[0014] As is clearly evident in FIGS. 1 and 2, interposed the outer
surface of fuel body 14 and the inner surface of container 12 is a
zone 16, of nominal spacing between these two structures, in which
zone, in accordance with the present invention, there is a
generally cylindrical jacket 18 which functions herein as an
elastomeric, heat-insulative, continuous-surface,
intumescence-behavior barrier jacket, or barrier, between container
12 and fuel 14. As illustrated in FIGS. 1 and 2, jacket 18 includes
a high-elastomeric body 18a, and embedded therewithin, a relatively
uniform distribution of intumescence elements 18b. Elements 18b
herein preferably take the form of sodium silicate crystals. These
elements (crystals), when exposed to intense heat, respond with a
popping and expanding intumescence behavior. Jacket 18 herein
substantially fills zone 16 between container 12 and fuel 14, and
may typically have a radial thickness, relative to previously
mentioned coincident axes 12b, 14b, of about 1/2-inches. This
jacket is formed to have an elastomeric body produced by a two-part
blend of combinable urethane elastomer materials which, after
blending, become chemically curable from an initial flowable and
very tacky state to a solid-body, high-elastomeric substance. This
two-part urethane elastomeric material may be made with different
specific starter materials, but one which has been found to be
extremely satisfactory is a two-part product made by Rhino Linings,
USA in San Diego, Calif., sold under the trademark TUFF
STUFF.RTM.FR. The distribution of intumescence elements, herein
preferably sodium silicate crystals, occupies the total volume of
jacket 18 by about 50%, with these crystals having a mesh size of
about 100-mesh.
[0015] Other kinds of intumescence materials which may be employed
include microencapsulated melamine polyphosphates, amorphous
silica, microencapsulated ammonium polyphosphates, and expandable
graphite.
[0016] Additionally, if desired, jacket 18 may be reinforced to
deal more tenaciously with intumescence behavior by having an
inclusion of fibrous material, such as glass or Kevlar.RTM.
strands/whiskers, such as the Kevlar.RTM. whiskers which are shown
in a small region 19 in FIG. 2.
[0017] The blended and distributed materials, including any
optionally introduced reinforcing fibres, which make up jacket 18
preferably are spray-applied to the inner surface 12a of container
12 to have the jacket features just described, with the outer
portion of jacket 18, i. e., that portion of the jacket which is in
contact with inner surface 12a, tenaciously bonding during spraying
to the container's inner surface. The inner, somewhat cylindrical
surface 18c in jacket 18, which surface generally circumsurrounds
previously mentioned axes 12b, 14b, effectively defines an elongate
cylindrical chamber 20 for receiving solid fuel body 14.
[0018] With rocket engine assembly 10 ready for use, when fuel body
14 is ignited, and when intense heat then begins to develop within
this fuel, several important mechanisms come into play with respect
to the way in which jacket 18 protects cylinder 12 against
catastrophic damage. First of all it is extremely important to note
that because of the nature of insulative jacket 18, and the fact
that this jacket is created by spraying as one continuum, or
continuous surface expanse, completely around and along inner
surface 12a of cylinder 12, there are no discontinuities, such as
those discussed earlier herein, to allow for easy penetration of
jacket 18 to attack cylinder-wall integrity. Secondly, any
heat-produced mechanical deformation which may take place in the
cylinder wall is "followed" immediately by the elastomeric body
portion of jacket 18 because of the tenacious bonding which exists
between cylinder wall surface 12a and jacket 18 during
spray-application of the materials making up jacket 18. A third
very important mechanism is that, essentially, that portion of
jacket 18 which confronts, and is in contact with, the burning body
of solid fuel produces, at the interfacial region between the
jacket and the fuel, intumescence behavior which causes,
effectively, the overall thickness of the jacket to tend to
increase in a manner which thereby tends to drive the source of
intense heat more distantly away (i.e., radially inwardly relative
to axes 12b, 14b) from inner surface 12a in cylinder 12.
[0019] FIGS. 4A, 4B and 4C generally illustrate this important
characteristic of intumescence behavior. In FIG. 4A, there is shown
a simplified illustration of cylinder 12 and adjoining jacket 18
under circumstances before any heat develops on the solid-fuel
facing side (the right side) of jacket 18 in this figure.
[0020] When solid fuel 14 begins to bum, and heat becomes generated
on the fuel-facing side of jacket 18, this heat causes the sodium
silicate crystals embedded within jacket 14 to begin swelling and
bursting in a region adjacent the burning fuel, such as is
illustrated at 22 generally in FIG. 4B. Illustrated here in a
somewhat exaggerated manner is the fact that this region 22, the
inner side of which can be thought of as being defined by an
intumescence-temperature front represented by dash-dot line 24 in
FIG. 4B, has caused the overall radial thickness of jacket 18 to
increase. In a way of somewhat simplistically describing this
intumescence behavioral feature of jacket 18, and augmenting what
was said earlier herein, one can think of front 24 as being a
crystal "popping" or "exploding and expanding" front effectively
defined by a temperature rise within jacket 18 which is sufficient
to cause sodium-silicate crystal-popping expansion.
[0021] FIG. 4C in the drawings, which is also an exaggerated
illustration, pictures a circumstance somewhat later in time than
that pictured in FIG. 4B, and specifically, a time by which front
24 has moved more deeply radially inwardly into jacket 18, with
consequent, additional thickening of jacket 18.
[0022] One can thus see that there is an important tendency of this
intumescence behavior to increase the distance between the region
of high, fuel-burning heat and the inner surface 12a of container
12 as fuel combustion continues. Accordingly, elastomeric jacket
18, in relation to its no-discontinuity and thickness-swelling
characteristics, is uniquely structured to minimize the likelihood
of any catastrophic damage occurring to container 12.
[0023] Turning attention finally to FIG. 3 in the drawings, what is
shown here is a modified version of jacket 18 in which, as in the
case of previously described jacket 18, there is an elastomeric
body 18a wherein resides an embedded distribution of sodium
silicate intumescence elements 18b. Here, however, elements 18b are
distributed within the body of jacket 12 with a non-uniform
density, and in particular, with a density gradient whereby the
density of these elements is greater in regions located close to
fuel 14 than it is in regions of the jacket more closely adjacent
container wall surface 12a. A very useful density gradient is one
wherein the higher-element-density region near fuel 14 has a
density preferably of about 50%-60%, and the lower-element-density
region near surface 12a has a density preferably of about
0%-20%.
[0024] From a methodologic point of view the invention can be
described as a method for minimizing, in a solid-fuel rocket, heat
damage to the wall of a solid-fuel, container during burning of
contained solid fuel, with this method including the steps of: (a)
placing between the container and contained fuel a structurally
continuous, heat-insulative barrier having an outer surface which
is adhered to the container, and an inner surface which faces the
contained solid fuel; and (b) during burning of the contained fuel,
utilizing container-wall surface adherence and jacket-material
elasticity in the barrier's outer surface to cause that surface to
follow any heat-created deformations that occur in the adjacent
container, and simultaneously utilizing the barrier's inner surface
to confront the burning solid fuel with elastomeric intumescence,
barrier-thickening behavior.
[0025] Still another way of expressing the present invention from a
methodologic point of view is to describe it as a method for
minimizing, in a solid-fuel rocket, heat damage to the wall of a
solid-fuel container during burning of contained, inwardly spaced,
solid fuel, including the steps of: (a) producing dual-interface,
continuous-presence, heat-insulative barriering in the zone
existing intermediate the container and the burning fuel, with such
barriering being characterized by (1) interfacially following any
heat-produced deformations in the container, and (2) interfacially
confronting the burning fuel with intumescence-driven, elastomeric
barrier-thickening.
* * * * *